From 431bde2c72311d5437e03bd84e613540e66ae40a Mon Sep 17 00:00:00 2001
From: wborgeaud <williamborgeaud@gmail.com>
Date: Fri, 4 Feb 2022 17:04:07 +0100
Subject: [PATCH] Fix number of quotient polys

---
 starky/src/fibonacci_stark.rs | 2 +-
 starky/src/prover.rs          | 6 +++---
 starky/src/stark.rs           | 6 ++++--
 starky/src/stark_testing.rs   | 6 +++---
 starky/src/verifier.rs        | 4 ++--
 5 files changed, 13 insertions(+), 11 deletions(-)

diff --git a/starky/src/fibonacci_stark.rs b/starky/src/fibonacci_stark.rs
index ce50dfd5..c77775e8 100644
--- a/starky/src/fibonacci_stark.rs
+++ b/starky/src/fibonacci_stark.rs
@@ -82,7 +82,7 @@ impl<F: RichField + Extendable<D>, const D: usize> Stark<F, D> for FibonacciStar
         todo!()
     }
 
-    fn degree(&self) -> usize {
+    fn constraint_degree(&self) -> usize {
         2
     }
 }
diff --git a/starky/src/prover.rs b/starky/src/prover.rs
index 2bea24ff..171ea92a 100644
--- a/starky/src/prover.rs
+++ b/starky/src/prover.rs
@@ -82,7 +82,7 @@ where
         .flat_map(|mut quotient_poly| {
             quotient_poly.trim();
             quotient_poly
-                .pad(degree << rate_bits)
+                .pad(degree * (stark.constraint_degree() - 1))
                 .expect("Quotient has failed, the vanishing polynomial is not divisible by `Z_H");
             // Split quotient into degree-n chunks.
             quotient_poly.chunks(degree)
@@ -123,7 +123,7 @@ where
         timing,
         "compute openings proof",
         PolynomialBatch::prove_openings(
-            &S::fri_instance(zeta, g, rate_bits, config.num_challenges),
+            &stark.fri_instance(zeta, g, rate_bits, config.num_challenges),
             initial_merkle_trees,
             &mut challenger,
             &fri_params,
@@ -162,7 +162,7 @@ where
 {
     let degree = 1 << degree_bits;
 
-    let max_degree_bits = log2_ceil(stark.degree() - 1);
+    let max_degree_bits = log2_ceil(stark.constraint_degree() - 1);
     assert!(
         max_degree_bits <= rate_bits,
         "Having constraints of degree higher than the rate is not supported yet."
diff --git a/starky/src/stark.rs b/starky/src/stark.rs
index 9721c203..8f112939 100644
--- a/starky/src/stark.rs
+++ b/starky/src/stark.rs
@@ -63,11 +63,12 @@ pub trait Stark<F: RichField + Extendable<D>, const D: usize>: Sync {
     );
 
     /// The maximum constraint degree.
-    fn degree(&self) -> usize;
+    fn constraint_degree(&self) -> usize;
 
     /// Computes the FRI instance used to prove this Stark.
     // TODO: Permutation polynomials.
     fn fri_instance(
+        &self,
         zeta: F::Extension,
         g: F::Extension,
         rate_bits: usize,
@@ -75,7 +76,8 @@ pub trait Stark<F: RichField + Extendable<D>, const D: usize>: Sync {
     ) -> FriInstanceInfo<F, D> {
         let no_blinding_oracle = FriOracleInfo { blinding: false };
         let trace_info = FriPolynomialInfo::from_range(0, 0..Self::COLUMNS);
-        let quotient_info = FriPolynomialInfo::from_range(1, 0..(1 << rate_bits) * num_challenges);
+        let quotient_info =
+            FriPolynomialInfo::from_range(1, 0..(self.constraint_degree() - 1) * num_challenges);
         let zeta_batch = FriBatchInfo {
             point: zeta,
             polynomials: [trace_info.clone(), quotient_info].concat(),
diff --git a/starky/src/stark_testing.rs b/starky/src/stark_testing.rs
index b8b31cf9..b28a206e 100644
--- a/starky/src/stark_testing.rs
+++ b/starky/src/stark_testing.rs
@@ -22,7 +22,7 @@ where
     [(); S::COLUMNS]:,
     [(); S::PUBLIC_INPUTS]:,
 {
-    let rate_bits = log2_ceil(stark.degree() + 1);
+    let rate_bits = log2_ceil(stark.constraint_degree() + 1);
 
     let wire_ldes = random_low_degree_matrix::<F>(S::COLUMNS, rate_bits);
     let size = wire_ldes.len();
@@ -68,13 +68,13 @@ where
         .collect::<Vec<_>>();
 
     let constraint_eval_degree = PolynomialValues::new(constraint_evals).degree();
-    let maximum_degree = WITNESS_SIZE * stark.degree() - 1;
+    let maximum_degree = WITNESS_SIZE * stark.constraint_degree() - 1;
 
     ensure!(
         constraint_eval_degree <= maximum_degree,
         "Expected degrees at most {} * {} - 1 = {}, actual {:?}",
         WITNESS_SIZE,
-        stark.degree(),
+        stark.constraint_degree(),
         maximum_degree,
         constraint_eval_degree
     );
diff --git a/starky/src/verifier.rs b/starky/src/verifier.rs
index b91fe457..b04ec684 100644
--- a/starky/src/verifier.rs
+++ b/starky/src/verifier.rs
@@ -98,7 +98,7 @@ where
     // So to reconstruct `t(zeta)` we can compute `reduce_with_powers(chunk, zeta^n)` for each
     // `quotient_degree_factor`-sized chunk of the original evaluations.
     for (i, chunk) in quotient_polys_zeta
-        .chunks(1 << config.fri_config.rate_bits)
+        .chunks(stark.constraint_degree() - 1)
         .enumerate()
     {
         ensure!(vanishing_polys_zeta[i] == z_h_zeta * reduce_with_powers(chunk, zeta_pow_deg));
@@ -108,7 +108,7 @@ where
     let merkle_caps = &[proof.trace_cap, proof.quotient_polys_cap];
 
     verify_fri_proof::<F, C, D>(
-        &S::fri_instance(
+        &stark.fri_instance(
             challenges.stark_zeta,
             F::primitive_root_of_unity(degree_bits).into(),
             config.fri_config.rate_bits,